The objective of this Shared Instrument Grant proposal is to obtain instrumentation capable of detecting changes in intracellular ion concentrations by detecting fluorescence from excitable cells loaded with appropriate dyes. Several investigators centered in the Department of Pharmacology need to use the instrumentation requested in order to address significant questions that are specific aims of their research. The specific equipment we wish to purchase consists of a Tracor Northern Fluoroplex III dual excitation fluorescence measuring system for biological samples coupled to a Nikon inverted microscope equipped for fluorescence and attached to both Photomultiplier and Video based Detection. Over the past several years there has been a very rapid growth in NIH funded cellular research at the University of Nevada School of Medicine. This growth has brought together a highly focused group of investigators whose interests center on excitable cells. In order to pursue our various studies of the regulation of cellular physiology by intracellular events, we require up-to-date research capabilities that we can not obtain as individuals. The Fluoroplex III System specified here, represents a fundamental capability that will perform multiple types of analyses. The strength of the equipment requested is that it is capable of three modes of use that will be complimentary. These are a macroscopic mode in which cellular fluorescence can be assessed in a cuvette, a microscopic mode in which fluorescence in a desired location in a cell can be measured with single or dual Photomultipliers, and finally, a video mode in which cellular fluorescence can be acquired with good spatial resolution in two dimensions. The major users of the equipment are a highly interactive group of NIH funded investigators that are studying various aspects of the regulation of contraction of smooth, cardiac, and skeletal muscles, targeted at the understanding of diseases such as cardiac failure, hypertension, asthma, bowel disease and muscular dystrophy. The Fluoroplex system will provide investigators at the University of Nevada with an invaluable research tool that will greatly increase our productivity and research competitiveness. The Dean of the University of Nevada School of Medicine is enthusiastic about this grant and has committed his resources to the installation, support and maintenance of the equipment.